Re: it isn't strange?!

*To*: mathgroup at smc.vnet.net*Subject*: [mg116133] Re: it isn't strange?!*From*: DrMajorBob <btreat1 at austin.rr.com>*Date*: Thu, 3 Feb 2011 05:29:01 -0500 (EST)

I will assume that "pb" means peanut butter. So here is your peanut butter: conditions = Reduce[Max[a, b] == Max[c, d], c, Reals] /. {And -> List, Or -> List} {{d < Max[a, b], c == Max[a, b]}, {d == Max[a, b], c <= Max[a, b]}} conditions /. {d -> 2, a -> 4, b -> 3, c -> 6} And @@@ % {{True, False}, {False, False}} {False, False} conditions /. {d -> 4, a -> 4, b -> 3, c -> 6} And @@@ % {{False, False}, {True, False}} {False, False} A tautology is a logical statement that's true for every value of the variables. Your conditions are NOT a tautology, as your two examples prove. Bobby On Wed, 02 Feb 2011 05:06:39 -0600, olfa <olfa.mraihi at yahoo.fr> wrote: > Hi Mathematica community, > > here is my pb: > > input: > Reduce[Max[a, b] == Max[c, d], c, Reals] > output: > (d < Max[a, b] && c == Max[a, b]) || (d == Max[a, b] && c <= Max[a, > b]) > > when testing this output with 2 initialisations: > d = 2 a = 4 b = 3 c = 6 here d < Max[4, 3] but c is not equal to > Max[4, 3] > > d = 4 a = 4 b = 3 c = 6 here d = Max[4, 3] but c is not <= to > Max[4, 3] > > where is the pb?! > -- DrMajorBob at yahoo.com